Study on Crystallization Kinetics of Polymer Ultra-thin Films ZHU Dunshen, SHOU Xingxian, CHEN Chao, CHEN Erqiang Department of Polymer Science and Engineering, College of Chemistry, Peking University, Beijing 100871, China The low molecular weight polyoxyethylene (PEO) fractions with double hydroxyl groups and single-ended hydroxyl groups in Beijing For the model system, we studied the crystallization kinetics of ultra-thin polymer films. Through a simple dilute solution static casting method, we can obtain a PEO ultrathin film with a thickness of less than 50 nm on the surface of mica. X-ray reflectance measurements (XR) and atomic force microscopy (AFM) experiments confirmed that the resulting PEO ultra-thin films had a "pseudo-infiltrated" melt structure, ie PEO formed a 4 to 5 nm wetting layer on the mica surface, while the excess PEO Because of the "self-enthalpy interaction", a mass of melt is formed on the infiltration layer. We used AFM to investigate the crystallization kinetics and crystal morphology of PEOs with "pseudo-infiltrated" melts in-situ. Experiments have shown that low molecular weight PEOs can grow an integer number of folded chain (IF) crystals on the mica surface. The IF crystals of double-ended hydroxyl-containing PEOs are round or dendritic, and the relationship between their transverse average size (R) and crystallization time (t) is: Rt 1/2, indicating that crystal growth is controlled by diffusion. Single-ended hydroxy-containing PEOs grow square or hexagonal IF crystals with a well-defined crystal growth plane whose kinetics are: R indicates crystal growth while controlled by diffusion and surface nucleation. We believe that the above-mentioned special PEO ultra-thin film crystallization behavior is caused by "false infiltration"

Melt structure is determined. During the crystallization process, the transport of the PEO chains to the front of the crystal growth is limited to a very thin wetting layer and must pass through a crystal/carcass interface with a width of only l2 nm. This makes the diffusion very slow and thus a decisive factor in controlling the crystal growth rate.

Influence of backbone chain stiffness and side chain length on phase transition behavior of comb-like macromolecules Shi Haifeng, Zhou Yong, Zhao Ying, Wang Yijin, Xu Duanfu State Key Laboratory of Polymer Physics and Chemistry, Chinese Academy of Sciences, Comb (comb) -likepolymers) as a class of special polymer, because they are between the traditional linear polymer and the dendrimer, and have different structural characteristics and properties with the traditional polymer, which attracted widespread attention. As a special type of "soft substance", its molecular shape is similar to that of the supramolecular self-assembly new substance. However, many molecular condensed state structures of the new substance still need to be clarified. Therefore, to study the condensed structure and phase transition behavior of comb-like macromolecules can enrich or deepen the differences between them and traditional macromolecular condensed structure. By studying the condensed structure and physicochemical properties of the comb-like polymers, the knowledge of molecular agglomerates in the mesophase in polymer sciences and the understanding of the characteristics of nanostructures can be enhanced. For this purpose, we chose two kinds of comb polymers with different main chain structures and rigidity (N-alkyl poly-p-phenylbenzamide with rigid backbone and N-alkyl polyethyleneimine with flexible backbone) as research objects. Investigate the phase transition behavior of the side chains during temperature changes, focusing on the effect of different backbone structures on the structure of the alkyl side chain, including the effect on the conformational transition and the change in the packing pattern of side chain molecular segments.